An image forming apparatus, for example, a color copy machine or printer, has a toner cartridge to supply toner to a developing device. The toner cartridge is removably attached to the body of the image forming apparatus. A user can easily replace the toner cartridge when toner in the toner cartridge is used up.
For example, a toner cartridge disclosed in Japanese Patent Publication (KOKAI) No. 2007-310146 has an elongated cylindrical cartridge body that houses toner, a stirring member housed within the cartridge body, and a screw arranged at the bottom of the cartridge body. The cartridge body has a filling port from which toner is put into the cartridge body, and a discharge port from which the toner is discharged toward the developing device. The stirring member rotates in the cartridge body and thereby stirs the toner. The screw rotates in the cartridge body and thereby moves the toner toward the discharge port.
When the toner in the cartridge body is decreased, a gap is generated between the inner surface of the cartridge body and the stirring member. The toner thus unavoidably remains adhering to the inner surface of the cartridge body. To deal with this, in the toner cartridge disclosed in the above Patent Publication, a scraper is attached to the stirring member. The scraper is formed by a flexible sheet member made of synthetic resin and is protruding from the stirring member toward the inner surface of the cartridge body. The scraper moves in contact with the inner surface of the cartridge body when the stirring member rotates. Thus, the toner adhering to the inner surface of the cartridge body is scraped off by the scraper and is fed into the screw. Therefore, the toner in the toner cartridge can be effectively used without being wasted.
In the toner cartridge of this type, it is desirable that the quantity of toner filling is increased to reduce the frequency of replacing the toner cartridge. As an attempt to increase the quantity of toner filling, a pair of toner housing portions is formed within the toner cartridge body. The toner housing portions are arranged side by side in the cartridge body and a stirring member is arranged in each toner housing portion. Each stirring member has a driving gear. The gears mesh with each other on the outside of the cartridge body. This meshing causes the stirring members to rotate in the opposite directions synchronously with each other.
In this configuration, the arrangement spacing between the stirring members is defined so that the stirring members do not interfere with each other in the cartridge body. However, if scrapers are attached to the outer circumferences of the stirring members, when the stirring members rotates, the scrapers of the stirring members may contact each other. If the scrapers are damaged by their contact with each other, small pieces and particles generated by the damage are carried into the developing device together with toner. The small pieces and particles may cause malfunction of the developing device and obstruct formation of a high-quality image.
Therefore, when arranging a pair of stirring members with scrapers side by side, it is necessary to avoid mutual interference of the scrapers. To this end, gears must be meshed with each other at a position where a phase difference along the rotating direction of the stirring members occurs between the scrapers. In other words, when assembling the toner cartridge, the operator must define the meshing position of the gears that rotate with the stirring members, while confirming the position of the scrapers. This assembling operation of the toner cartridge requires a great amount of time and labor.